Winter in New Hampshire a time for survival of the fittest

White-tailed deer are supremely adapted to long, cold winters in New Hampshire forests - as are lots of other native species. Many newcomers - human as well as animal - are decidedly less so. Garrett Evans Photography

"If you don't like the weather in New England now, just wait a few minutes." - Mark Twain

The weather roller coaster heaved from "Polar Vortex" to January thaw. And, for some folks, not a moment too soon. Less than three weeks into the new year, the less winter-hardy already were exhibiting early-onset symptoms of acute cabin fever. Not a good sign with March seeming like some distant galaxy.

Second only to politics, New Hampshire residents are obsessed with weather. Weather is the lowest common denominator. Nearly everyone experiences similar hardships - winter driving, shoveling, plowing, heating - yet some voice more complaints than others. Big storms and extreme temperatures boost TV ratings. Weather sells. But nobody can do anything other than add it the list of certainties: "weather, death and taxes" - often in that order.

This year's stretch of brutal January temperatures elicited Armageddon-like predictions for all-time record-low temperatures. Nevertheless, some cranky Yankees still prefer to live here and earn their stripes rather than move to a more temperate (and densely populated) locale. Extreme winter weather thins the herd. Those remaining here prefer weather woes to traffic jams.

Subzero confers bragging rights. We mock Miami shivering in 60-degree horror the same way North Dakotans generally regard everyone else. It's cold comfort to be this tough. "If you're a sissy, move south" is implied when thermometer photos make the news.

With the weather pattern now poised to return to normal (whatever that is), I'm reminded that monthly averages are determined by extremes without regard to how far apart they lie. I'm waiting for the Granite State version of the insurance ad featuring "Mayhem," who surely must spend January here in New Hampshire.

Arctic temperatures have a sunny side. Successive nights of double-digit subzero temperatures may actually be beneficial to the state's forests. A silver lining to the evil "Polar Vortex" is that some equally nasty forest pests are not particularly cold-hardy enough to survive at 10-below or 15-below temperatures. The bad bugs may not want to live in New Hampshire after all.

According to Kyle Lombard, forest health program specialist with the state Division of Forests and Lands, northward expansion of exotic insects is checked by their limited cold tolerance.

"The colder the better!" he said. "Our environment limits many forest pests to other (warmer) regions. Low winter temperatures are one of the most important factors determining insects' ranges.

"Our most troublesome forest pests face cold-hardiness limits. Hemlock Woolly Adelgid populations regularly have 30 to 80 percent winter kill depending on the year. No Balsam Woolly Adelgid damage has been found above 2,000 feet in elevation in New Hampshire, likely due to low winter temperatures. Gypsy moth egg mass survival fluctuates wildly from 10 to 70 percent due to cold-temperature extremes. Winter moth, forest tent caterpillar and red pine scale all have limits to what they can survive. Unusually cold conditions for prolonged periods limit these pest populations."

The picture becomes more complex with site-scale factors, which mitigate how much cold the overwintering insects experience.

"Aspect, thermal mass of a tree, time of year, duration of cold, health of insects, snow cover, tree density, and elevation are all factors," Lombard said.

"The reality is, no amount of deep cold will likely stop EAB," he said. "Beetles spend winters jacked up on glycol and antifreeze protein while buried deep under a warm blanket of thick ash bark, so winter temps are nothing more than a nuisance unlikely to kill any significant percentage of their population."

Overwintering deer ticks may be reduced by extreme cold. That good news translates into a reduction in future rates of human Lyme disease. A lack of heavy oak acorn crops statewide is just as important, the effect being the crashing populations of woodland mice, the primary vectors for tiny deer tick nymphs.

White-tailed deer are superbly adapted to long, cold winters, as are many other native species. Many recent newcomers are less so.

Deer don't experience severe winter tick infestations. They tend to groom off questing winter ticks in autumn. And deer can cope with cold. Layers of hollow, air-trapping fur insulates them to the extent that they lie down in snow beds in sheltered locales.

Winter severity is more a timing issue when protracted late-season deep snow pack limits deer travel and constrains food foraging opportunities. By late winter, weeks of slow starvation weakens deer, culling the herd just as hungry coyotes scavenge and hunt in preparation for the rigors of their April pup birthing. No carcass is wasted, and the timing seems elegant.

In winter forests devoid of low browse, chainsaws toll a deer dinner bell. Local logging operations temporarily increase availability of natural foods at ground level, drawing in hungry deer. North Country loggers report deer not even waiting for saws to shut down before moving into the harvested area to feed on fresh slash - tree tops and branches left on top of the snow.

Deer tracks on my woodlot invariably lead to where I've been cutting wood. Coyote tracks will soon follow.

Said Sarah Smith, forest industry specialist for the UNH Cooperative Extension, "A good freeze-up allows loggers to access areas that remain soggy the rest of the year. Winter truck roads are stable and hold the weights of full loads. Wood markets are generally strong as mills build inventory to carry them through the spring mud season, when logging operations generally cease."

While last week's January thaw was a nice respite, there are many good reasons to hope it was merely temporary. Good old-fashioned, arctic winter weather is good for New England natives ... perhaps less so for more recent transplants.

The weather pattern changed three times in the course of writing this column. If you have weather complaints, contact your local meteorologist. If you have weather kudos, I accept!

"Forest Journal" appears every other week in the New Hampshire Sunday News. Naturalist Dave Anderson is Director of Education and Volunteer Services for the Society for the Protection of New Hampshire Forests. Email him at danderson@forestsociety.org or through the Forest Society Web site: forestsociety.org.